WIP: Assdraw

Include assdraw in aegisub, like in windows builds. Focus on the Linux/BSD build for the moment because it's where I can test

assdraw/Makefile

@@ -41,4 +41,4 @@ assdraw_SOURCES := \
 assdraw_CPPFLAGS := -I$(d)
 assdraw_CXXFLAGS := $(CXXFLAGS_WX)
 assdraw_OBJ      := $(assdraw_SOURCES:.cpp=.o)
-assdraw_LIBS     := $(LIBS_WX)
+assdraw_LIBS     := $(LIBS_WX) $(LIBS_AGG)